JP4128163B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a sipe is engraved on a tread surface, and more particularly to a pneumatic tire in which braking performance and the like are improved after the middle period of wear.

  In a pneumatic tire, in addition to main grooves and lateral grooves, a narrower sipe has been cut on the tread surface to improve drainage. Further, in studless tires intended for running on icy and snowy roads, more sipes have been cut and the edge effect of these sipes has been demonstrated to improve braking / driving performance and turning performance.

As shown in FIG. 1 (b), the sipe 11 was often carved with a constant thickness. For example, in the sipe carved in the tire width direction, the block collapses due to the longitudinal force applied during braking or the like, and the braking force is generated by the edge effect of the sipe 11. Moreover, if the sipe is blocked uniformly, the edge effect and the water removal effect that the sipe should originally exhibit are reduced. In order to solve such a problem, in the pneumatic tire disclosed in Patent Document 1, a wide portion having a thickness larger than that of other portions is provided in a sipe to improve an edge effect and a water removal effect.
Japanese Patent Laid-Open No. 9-272312

  In a sipe having a constant thickness, when wear progresses and the height of the block decreases, the rigidity of the block increases and the collapse of the block decreases. As a result, the edge effect becomes insufficient, and the braking performance and the like may gradually deteriorate as wear progresses. In addition, when the sipe thickness is increased in advance, the collapse of the sipe becomes too large at the initial stage of wear, and the edge effect may be lowered.

  In the pneumatic tire according to Patent Literature 1, since the wide portion extends from the tread surface to the sipe bottom, it has been difficult to maintain an appropriate collapse from the early wear stage to the late wear stage. In addition, since the wide portion is at both ends of the sipe, uneven wear may occur at the edge of the block.

  Accordingly, an object of the present invention is to generate a suitable fall from the initial stage of wear to the end stage of wear, exhibit a good edge effect, and improve tire performance.

As a result of intensive studies to solve the above problems, the invention according to claim 1 is a pneumatic tire in which a sipe is carved on a tread surface.
The sipe has a wide portion, the wide portion extends from a location in D1 by the depth direction from the surface of the tread to the beginning sipe bottom, D1 is Ri 20% to 80% der depth D of the sipe, the The wide portion was terminated at a position entering L1 from the end of the sipe, and a pneumatic tire with L1 of 1 mm to 5 mm was used.

  After the middle period of wear, the rigidity of land portions (blocks and ribs) engraved with sipe is increased, but since wide portions appear, proper fall of the land portions is ensured. Therefore, it is possible to secure an appropriate fall from the initial wear stage to the final wear stage, so that the edge effect of the sipe is exhibited without causing a reduction in the contact area. As a result, tire performance such as braking performance is improved.

  When L1 is set to 1 mm to 5 mm, more preferably 2 mm to 3 mm, the rigidity of the sipe end portion does not decrease, so uneven uneven wear is suppressed. In particular, when the sipe end portion is open in a groove that divides the land portion, the rigidity of the edge portion of the land portion does not decrease, so that uneven uneven wear is suppressed.

  According to the present invention, the sipe is provided with a wide portion so that the width of the sipe increases as wear progresses. As a result, it is possible to ensure a proper fall from the beginning of wear to the end of wear, so that the edge effect of sipe is exhibited without causing a reduction in the contact area, and tire performance such as braking performance is improved.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. Hereinafter, an example in which a sipe is engraved on the block will be described. Fig.1 (a) is a perspective view which shows the sipe carved in the pneumatic tire which concerns on this invention. The sipe 1 has a linear opening 2 and is carved into land portions such as blocks and ribs. The sipe 1 includes a wide portion 3, and the wide portion 3 starts from a position S in the depth direction by D 1 from the surface of the tread T and extends to the sipe bottom 4.

  FIG. 2A shows a state where the sipe 1 is carved in the tire width direction W on the block 10. The end portion of the sipe 1 is open to the groove 21 that defines the block 10, but the wide portion 3 is terminated at a position that is inward by L 1 from the end portion of the sipe 1.

  In the initial stage of wear, the wide portion 3 does not appear on the surface of the tread T, but the rigidity of the block 10 is low, so that the block 10 falls down moderately. In addition, after the middle stage of wear, the rigidity of the block 10 is increased, but since the wide portion 3 appears, an appropriate collapse of the block 10 is ensured. Accordingly, since the block 10 can be properly fallen from the initial wear stage to the final wear stage, the edge effect of the sipe 1 is exhibited without causing a reduction in the contact area.

  If L1 is set to 1 mm to 5 mm, more preferably 2 mm to 3 mm, the rigidity of the end portion of the sipe 1 is not lowered, so that uneven wear at the edge of the block 10 is suppressed. Further, D1 is preferably 20% to 80% of the sipe depth D. If it is less than 20%, the rigidity of the block 10 becomes too low at the initial stage of wear, and the collapse may increase. If it exceeds 80%, rigidity reduction after the middle stage of wear may be insufficient.

  The thickness t1 of the wide portion 3 is not particularly limited. For example, when the thickness t of the sipe 1 is 0.3 mm to 0.5 mm, the thickness t1 of the wide portion 3 is set to 0.6 mm to 1.2 mm. Preferably, 0.6 mm to 0.8 mm is more preferable.

  Further, the sipe 1 may be an open sipe having both ends opened as shown, a closed sipe having both ends closed, or a single open sipe having only one end opened. At the closed end, the end of the wide portion 3 may be terminated at the same position as the end of the sipe 1 and L1 may be zero.

  As an example, a pneumatic tire according to the present invention and a pneumatic tire according to a conventional example were prototyped and performance evaluation was performed. The tire according to the example includes the block illustrated in FIG. 2A, and the tire according to the conventional example includes the block illustrated in FIG. The shape and dimensions of the sipe were as shown in Table 1. The tire size was 195 / 65R15, and the performance was evaluated by mounting it on a 2000 ccFF sedan type passenger car.

  In Table 1, ice performance is the reciprocal of the ABS braking distance from 40 km / h on the ice road surface when new and worn. It is represented by an index with the conventional example at the time of a new product as 100, and the larger the number, the better the performance. In addition, the time of abrasion means the state where the tread has been worn by 50% of the sipe depth D.

  According to Table 1, in the conventional example, when the wear progresses, the collapse is insufficient and the braking performance is deteriorated. In the embodiment, since the sipe is provided with the wide portion, the proper falling is maintained, and the edge effect is exhibited and the braking performance is maintained even after the middle stage of wear.

  The case where the sipe is cut in the tire width direction has been described above, but the sipe may be cut in a tire circumferential direction or an oblique direction. In the case of a sipe extending in the tire circumferential direction, the turning performance is improved. In the case of a sipe extending in an oblique direction, braking performance and turning performance are improved. Further, the sipe may be a sipe having a waveform in addition to a straight sipe.

(A) is a perspective view of the sipe of the pneumatic tire which concerns on this invention, (b) shows the perspective view of the sipe of the pneumatic tire which concerns on a prior art example, respectively. It is a figure which shows the block in which the sipe was engraved, (a) shows the block which concerns on an Example, (b) shows the block which concerns on a prior art example.

Explanation of symbols

1 Sipe 2 Opening 3 Wide 10 Block

Claims (1)

In pneumatic tires with sipe carved on the tread surface,
The sipe has a wide portion, the wide portion extends from a location in D1 by the depth direction from the surface of the tread to the beginning sipe bottom, D1 is Ri 20% to 80% der depth D of the sipe, the The wide tire terminates at a position entering L1 from the end of the sipe, and L1 is 1 to 5 mm .

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